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Why Beans?

April 18, 2014

If you start investigating Sonoran Desert plants, including trees and shrubs, you’ll find quite a few members of the bean family (Fabaceae) represented.

Palo Verde blossoms

Palo Verde blossoms

That may seem surprising. Why beans? At first glance, your average garden variety green bean plant does not seem especially deserty.

So let’s start with a hidden feature that might be useful in a desert—to deal with poor soil, beans have come up with a clever friendship—they have symbionts, associates, little bacteria that live in nodules, little bumps, in their roots. The beans provide water and sugars to the bacteria, and the bacteria “fix” nitrogen from the soil, turning it into a form the bean plants can use.

And that’s one reason beans are good for you—because of the nitrogen from their little friends, they can make certain essential amino acids, parts of proteins.

Grains like corn or wheat or rice make different amino acids. And it is important for us to eat them together with legumes, another name for beans, to get whole nutrition in one meal. So, for example, we dine on beans and rice, or beans in corn tacos or wheat tortillas, or baked beans with toast, or even a peanut butter sandwich, since peanuts are also a legume.

Humans figured this out a long long time ago, and in fact, they even grew grains and beans together. An essential core of Native American gardens all over North and South America was the trio of beans, corn and squash. The corn provides scaffolding for the beans to climb, and the remains of the bean plants are a source of usable nitrogen for the next year’s corn and squash. To this day, these three continue to play a big role in our gardens, as well as in those huge gardens known as farms.

It turns out that beans also have a bunch of other cool skills for the hot desert—stay tuned!

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